Change dart2js RegExp to keep global/anchored versions inside the JSRegExp.

Instead of creating new JSRegExp objects for global regexps, it now just does
a global exec on a native global regexp stored in the same object.
This also avoids having the wrong JSRegExp object as the Match `pattern` field.

Changed to not duplicate fields available on the native regexp or native match.

Review URL:

git-svn-id: 260f80e4-7a28-3924-810f-c04153c831b5
2 files changed